Make GeneratorHybrid a singleton (#14737)

* Make Generators list static

* Made GeneratorHybrid a singleton

Author: jackal1-66

Generators/include/Generators/GeneratorHybrid.h

@@ -54,8 +54,11 @@ class GeneratorHybrid : public Generator
 {
 
  public:
-  GeneratorHybrid(const std::string& inputgens);
-  ~GeneratorHybrid();
+  GeneratorHybrid& operator=(const GeneratorHybrid&) = delete;
+  GeneratorHybrid(const GeneratorHybrid&) = delete;
+
+  // Singleton access method
+  static GeneratorHybrid& Instance(const std::string& inputgens = "");
 
   Bool_t Init() override;
   Bool_t generateEvent() override;
@@ -66,8 +69,11 @@ class GeneratorHybrid : public Generator
   Bool_t confSetter(const auto& gen);
   template <typename T>
   std::string jsonValueToString(const T& value);
+  std::vector<std::shared_ptr<o2::eventgen::Generator>> const& getGenerators() { return gens; }
 
  private:
+  GeneratorHybrid(const std::string& inputgens);
+  ~GeneratorHybrid();
   o2::eventgen::Generator* currentgen = nullptr;
   std::vector<std::shared_ptr<o2::eventgen::Generator>> gens;
   const std::vector<std::string> generatorNames = {"extkinO2", "evtpool", "boxgen", "external", "hepmc", "pythia8", "pythia8pp", "pythia8hi", "pythia8hf", "pythia8powheg"};

Generators/src/GeneratorFactory.cxx

@@ -284,8 +284,8 @@ void GeneratorFactory::setPrimaryGenerator(o2::conf::SimConfig const& conf, Fair
       LOG(fatal) << "Configuration file for hybrid generator does not exist";
       return;
     }
-    auto hybrid = new o2::eventgen::GeneratorHybrid(config);
-    primGen->AddGenerator(hybrid);
+    auto& hybrid = o2::eventgen::GeneratorHybrid::Instance(config);
+    primGen->AddGenerator(&hybrid);
 #endif
   } else {
     LOG(fatal) << "Invalid generator";

Generators/src/GeneratorHybrid.cxx

@@ -23,6 +23,12 @@ namespace o2
 namespace eventgen
 {
 
+GeneratorHybrid& GeneratorHybrid::Instance(const std::string& inputgens)
+{
+  static GeneratorHybrid instance(inputgens);
+  return instance;
+}
+
 GeneratorHybrid::GeneratorHybrid(const std::string& inputgens)
 {
   // This generator has trivial unit conversions